With the development of television technology, a liquid-crystal television becomes gradually a main stream in television market due to its advantages of large screen, low thickness and high definition and so on. At present, a liquid-crystal television set is directly connected to mains via a power supply line in general, and converts alternative current (AC) mains inputted to the television set into a direct current (DC) voltage needed for respective circuits of the television set (such as signal circuit, illumination circuit, etc.) by means of a voltage conversion circuit inside the television set to provide operating power supply for the respective circuits in the television set.
As man-machine interaction deepens and touch screen television sets emerge in the market, the requirement for protection against electric shock of the television set is continuously increased. At present, the television set is directly connected to the mains mostly for use. Processes of rectifying from the mains to the operating voltage and voltage dropping are realized by the voltage conversion circuit integrated with the television set. As such, danger of electric shock of the human body would occur easily, in particular in the process of assembling the television set.